What is a blighted ovum (anembryonic pregnancy)?

Blighted Ovum (Anembryonic Pregnancy)

A blighted ovum is an outdated term that should be replaced with "anembryonic pregnancy," which refers to a specific type of early pregnancy loss (EPL) where a gestational sac measuring 25 mm or larger develops without an embryo. 1

Modern Terminology and Definition

According to the Society of Radiologists in Ultrasound (SRU) consensus recommendations:

• The term "blighted ovum" should be avoided in clinical practice and reporting 1
• The preferred term is "anembryonic pregnancy" or "diagnostic of early pregnancy loss (EPL)" 1
• Specifically, an anembryonic pregnancy is defined as:
  • A gestational sac measuring 25 mm or larger without an embryo
  • OR absence of an embryo on serial examinations obtained at discriminatory time intervals 1

Diagnostic Criteria

Anembryonic pregnancy is diagnosed when:

• Mean sac diameter (MSD) ≥25 mm with no embryo visible on transvaginal ultrasound 2
• OR absence of embryo with cardiac activity ≥14 days after visualization of a gestational sac with no yolk sac 2

Pathophysiology

An anembryonic pregnancy occurs when:

• A fertilized egg implants in the uterus
• The placental tissue and gestational sac begin to develop
• The embryo either fails to develop or stops developing very early and is reabsorbed
• The pregnancy sac continues to grow for a period of time despite the absence of an embryo

Clinical Presentation

Patients with anembryonic pregnancy may experience:

• Vaginal bleeding or spotting
• Abdominal cramping
• Absence of expected pregnancy symptoms or diminishing symptoms
• In some cases, no symptoms at all until diagnosis on routine ultrasound

Management Options

Management approaches for anembryonic pregnancy include:

1. Expectant management: Waiting for natural miscarriage

   • Appropriate for stable patients without excessive bleeding or signs of infection
   • Requires follow-up to confirm complete expulsion

2. Medical management: Using medications to induce miscarriage

   • May be considered when the patient prefers not to wait for spontaneous abortion
   • Or when complete expulsion doesn't occur within the expected timeframe 2

3. Surgical management: Suction dilation and curettage (D&C)

   • Considered when the patient prefers immediate resolution
   • Or when excessive bleeding, infection, or significant emotional distress occurs 2

Important Considerations

• Hormonal levels (hCG, progesterone, estradiol) in anembryonic pregnancies can be variable and sometimes indistinguishable from normal pregnancies 3
• Premature diagnosis should be avoided without meeting established criteria
• Follow-up ultrasound is essential to confirm diagnosis and complete expulsion for expectant or medical management 2
• Advanced maternal age appears to be a risk factor for anembryonic pregnancy 4

Caution in Diagnosis

• The SRU and American College of Obstetricians and Gynecologists advise against premature diagnosis of EPL without meeting established criteria 2
• Immediate intervention should not occur before confirming diagnosis with follow-up ultrasound to prevent misdiagnosis and unnecessary treatment 2

Remember that modern terminology emphasizes using "anembryonic pregnancy" or "early pregnancy loss" rather than the outdated term "blighted ovum" to describe this condition.